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RFC 5213

 Errata 
Proposed STD
Pages: 92
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Proxy Mobile IPv6

Part 1 of 4, p. 1 to 17
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Network Working Group                                 S. Gundavelli, Ed.
Request for Comments: 5213                                      K. Leung
Category: Standards Track                                          Cisco
                                                          V. Devarapalli
                                                                Wichorus
                                                            K. Chowdhury
                                                        Starent Networks
                                                                B. Patil
                                                                   Nokia
                                                             August 2008


                           Proxy Mobile IPv6

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Abstract

   Network-based mobility management enables IP mobility for a host
   without requiring its participation in any mobility-related
   signaling.  The network is responsible for managing IP mobility on
   behalf of the host.  The mobility entities in the network are
   responsible for tracking the movements of the host and initiating the
   required mobility signaling on its behalf.  This specification
   describes a network-based mobility management protocol and is
   referred to as Proxy Mobile IPv6.

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Table of Contents

   1.  Introduction .................................................  4
   2.  Conventions and Terminology  .................................  5
     2.1.  Conventions Used in This Document  .......................  5
     2.2.  Terminology  .............................................  5
   3.  Proxy Mobile IPv6 Protocol Overview  .........................  9
   4.  Proxy Mobile IPv6 Protocol Security  ......................... 15
     4.1.  Peer Authorization Database (PAD) Example Entries  ....... 16
     4.2.  Security Policy Database (SPD) Example Entries ........... 17
   5.  Local Mobility Anchor Operation  ............................. 17
     5.1.  Extensions to Binding Cache Entry Data Structure ......... 18
     5.2.  Supported Home Network Prefix Models ..................... 19
     5.3.  Signaling Considerations ................................. 20
       5.3.1.  Processing Proxy Binding Updates ..................... 20
       5.3.2.  Initial Binding Registration (New Mobility Session) .. 22
       5.3.3.  Binding Lifetime Extension (No Handoff)  ............. 23
       5.3.4.  Binding Lifetime Extension (After Handoff) ........... 24
       5.3.5.  Binding De-Registration  ............................. 24
       5.3.6.  Constructing the Proxy Binding Acknowledgement
               Message  ............................................. 25
     5.4.  Multihoming Support  ..................................... 27
       5.4.1.  Binding Cache Entry Lookup Considerations  ........... 28
     5.5.  Timestamp Option for Message Ordering  ................... 34
     5.6.  Routing Considerations ................................... 37
       5.6.1.  Bi-Directional Tunnel Management ..................... 37
       5.6.2.  Forwarding Considerations  ........................... 38
       5.6.3.  Explicit Congestion Notification (ECN)
               Considerations for Proxy Mobile IPv6 Tunnels ......... 39
     5.7.  Local Mobility Anchor Address Discovery  ................. 40
     5.8.  Mobile Prefix Discovery Considerations ................... 40
     5.9.  Route Optimization Considerations  ....................... 41
   6.  Mobile Access Gateway Operation  ............................. 41
     6.1.  Extensions to Binding Update List Entry Data Structure ... 42
     6.2.  Mobile Node's Policy Profile ............................. 43
     6.3.  Supported Access Link Types  ............................. 44
     6.4.  Supported Address Configuration Modes  ................... 44
     6.5.  Access Authentication and Mobile Node Identification ..... 45
     6.6.  Acquiring Mobile Node's Identifier ....................... 45
     6.7.  Home Network Emulation ................................... 46
     6.8.  Link-local and Global Address Uniqueness ................. 46
     6.9.  Signaling Considerations ................................. 48
       6.9.1.  Binding Registrations  ............................... 48
       6.9.2.  Router Solicitation Messages ......................... 56
       6.9.3.  Default-Router ....................................... 57
       6.9.4.  Retransmissions and Rate Limiting  ................... 58
       6.9.5.  Path MTU Discovery ................................... 59
     6.10. Routing Considerations ................................... 60

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       6.10.1. Transport Network  ................................... 60
       6.10.2. Tunneling and Encapsulation Modes  ................... 61
       6.10.3. Local Routing  ....................................... 62
       6.10.4. Tunnel Management  ................................... 62
       6.10.5. Forwarding Rules ..................................... 62
     6.11. Supporting DHCP-Based Address Configuration on the
           Access Link  ............................................. 64
     6.12. Home Network Prefix Renumbering  ......................... 66
     6.13. Mobile Node Detachment Detection and Resource Cleanup  ... 66
     6.14. Allowing Network Access to Other IPv6 Nodes  ............. 67
   7.  Mobile Node Operation  ....................................... 67
     7.1.  Moving into a Proxy Mobile IPv6 Domain ................... 67
     7.2.  Roaming in the Proxy Mobile IPv6 Domain  ................. 69
   8.  Message Formats  ............................................. 69
     8.1.  Proxy Binding Update Message ............................. 69
     8.2.  Proxy Binding Acknowledgement Message  ................... 71
     8.3.  Home Network Prefix Option ............................... 72
     8.4.  Handoff Indicator Option ................................. 73
     8.5.  Access Technology Type Option  ........................... 74
     8.6.  Mobile Node Link-layer Identifier Option ................. 76
     8.7.  Link-local Address Option  ............................... 77
     8.8.  Timestamp Option ......................................... 77
     8.9.  Status Values  ........................................... 78
   9.  Protocol Configuration Variables ............................. 80
     9.1.  Local Mobility Anchor - Configuration Variables  ......... 80
     9.2.  Mobile Access Gateway - Configuration Variables  ......... 81
     9.3.  Proxy Mobile IPv6 Domain - Configuration Variables ....... 82
   10. IANA Considerations  ......................................... 83
   11. Security Considerations  ..................................... 84
   12. Acknowledgements ............................................. 85
   13. References ................................................... 86
     13.1. Normative References ..................................... 86
     13.2. Informative References ................................... 87
   Appendix A.  Proxy Mobile IPv6 Interactions with AAA
                Infrastructure  ..................................... 89
   Appendix B.  Routing State ....................................... 89

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1.  Introduction

   IP mobility for IPv6 hosts is specified in Mobile IPv6 [RFC3775].
   Mobile IPv6 requires client functionality in the IPv6 stack of a
   mobile node.  Exchange of signaling messages between the mobile node
   and home agent enables the creation and maintenance of a binding
   between the mobile node's home address and its care-of address.
   Mobility as specified in [RFC3775] requires the IP host to send IP
   mobility management signaling messages to the home agent, which is
   located in the network.

   Network-based mobility is another approach to solving the IP mobility
   challenge.  It is possible to support mobility for IPv6 nodes without
   host involvement by extending Mobile IPv6 [RFC3775] signaling
   messages between a network node and a home agent.  This approach to
   supporting mobility does not require the mobile node to be involved
   in the exchange of signaling messages between itself and the home
   agent.  A proxy mobility agent in the network performs the signaling
   with the home agent and does the mobility management on behalf of the
   mobile node attached to the network.  Because of the use and
   extension of Mobile IPv6 signaling and home agent functionality, this
   protocol is referred to as Proxy Mobile IPv6 (PMIPv6).

   Network deployments that are designed to support mobility would be
   agnostic to the capability in the IPv6 stack of the nodes that it
   serves.  IP mobility for nodes that have mobile IP client
   functionality in the IPv6 stack as well as those nodes that do not,
   would be supported by enabling Proxy Mobile IPv6 protocol
   functionality in the network.  The advantages of developing a
   network-based mobility protocol based on Mobile IPv6 are:

   o  Reuse of home agent functionality and the messages/format used in
      mobility signaling.  Mobile IPv6 is a mature protocol with several
      implementations that have undergone interoperability testing.

   o  A common home agent would serve as the mobility agent for all
      types of IPv6 nodes.

   The problem statement and the need for a network-based mobility
   protocol solution has been documented in [RFC4830].  Proxy Mobile
   IPv6 is a solution that addresses these issues and requirements.

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2.  Conventions and Terminology

2.1.  Conventions Used in This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

2.2.  Terminology

   All the general mobility-related terms used in this document are to
   be interpreted as defined in the Mobile IPv6 base specification
   [RFC3775].

   This document adopts the terms, Local Mobility Anchor (LMA) and
   Mobile Access Gateway (MAG) from the NETLMM Goals document [RFC4831].
   This document also provides the following context-specific
   explanation to the following terms used in this document.

   Proxy Mobile IPv6 Domain (PMIPv6-Domain)

      Proxy Mobile IPv6 domain refers to the network where the mobility
      management of a mobile node is handled using the Proxy Mobile IPv6
      protocol as defined in this specification.  The Proxy Mobile IPv6
      domain includes local mobility anchors and mobile access gateways
      between which security associations can be set up and
      authorization for sending Proxy Binding Updates on behalf of the
      mobile nodes can be ensured.

   Local Mobility Anchor (LMA)

      Local Mobility Anchor is the home agent for the mobile node in a
      Proxy Mobile IPv6 domain.  It is the topological anchor point for
      the mobile node's home network prefix(es) and is the entity that
      manages the mobile node's binding state.  The local mobility
      anchor has the functional capabilities of a home agent as defined
      in Mobile IPv6 base specification [RFC3775] with the additional
      capabilities required for supporting Proxy Mobile IPv6 protocol as
      defined in this specification.

   Mobile Access Gateway (MAG)

      Mobile Access Gateway is a function on an access router that
      manages the mobility-related signaling for a mobile node that is
      attached to its access link.  It is responsible for tracking the
      mobile node's movements to and from the access link and for
      signaling the mobile node's local mobility anchor.

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   Mobile Node (MN)

      Throughout this document, the term mobile node is used to refer to
      an IP host or router whose mobility is managed by the network.
      The mobile node may be an IPv4-only node, IPv6-only node, or a
      dual-stack node and is not required to participate in any IP
      mobility related signaling for achieving mobility for an IP
      address that is obtained in that Proxy Mobile IPv6 domain.

   LMA Address (LMAA)

      The global address that is configured on the interface of the
      local mobility anchor and is the transport endpoint of the bi-
      directional tunnel established between the local mobility anchor
      and the mobile access gateway.  This is the address to which the
      mobile access gateway sends the Proxy Binding Update messages.
      When supporting IPv4 traversal, i.e., when the network between the
      local mobility anchor and the mobile access gateway is an IPv4
      network, this address will be an IPv4 address and will be referred
      to as IPv4-LMAA, as specified in [IPV4-PMIP6].

   Proxy Care-of Address (Proxy-CoA)

      Proxy-CoA is the global address configured on the egress interface
      of the mobile access gateway and is the transport endpoint of the
      tunnel between the local mobility anchor and the mobile access
      gateway.  The local mobility anchor views this address as the
      care-of address of the mobile node and registers it in the Binding
      Cache entry for that mobile node.  When the transport network
      between the mobile access gateway and the local mobility anchor is
      an IPv4 network and if the care-of address that is registered at
      the local mobility anchor is an IPv4 address, the term, IPv4-
      Proxy-CoA is used, as specified in [IPV4-PMIP6].

   Mobile Node's Home Network Prefix (MN-HNP)

      The MN-HNP is a prefix assigned to the link between the mobile
      node and the mobile access gateway.  More than one prefix can be
      assigned to the link between the mobile node and the mobile access
      gateway, in which case, all of the assigned prefixes are managed
      as a set associated with a mobility session.  The mobile node
      configures its interface with one or more addresses from its home
      network prefix(es).  If the mobile node connects to the Proxy
      Mobile IPv6 domain through multiple interfaces, simultaneously,
      each of the attached interfaces will be assigned a unique set of
      home network prefixes, and all the prefixes assigned to a given
      interface of a mobile node will be managed under one mobility
      session.  For example, home network prefixes P1 and P2 assigned to

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      interface I1 will be managed under one mobility session and
      prefixes P3, P4, and P5 assigned to interface I2 of the mobile
      node will be managed under a different mobility session.
      Additionally, in some configurations the assigned prefix can be of
      128-bit prefix length.

   Mobile Node's Home Address (MN-HoA)

      MN-HoA is an address from a mobile node's home network prefix.
      The mobile node will be able to use this address as long as it is
      attached to the access network that is in the scope of that Proxy
      Mobile IPv6 domain.  If the mobile node uses more than one address
      from its home network prefix(es), any one of these addresses is
      referred to as mobile node's home address.  Unlike in Mobile IPv6
      where the home agent is aware of the home address of the mobile
      node, in Proxy Mobile IPv6, the mobility entities are only aware
      of the mobile node's home network prefix(es) and are not always
      aware of the exact address(es) that the mobile node configured on
      its interface from its home network prefix(es).  However, in some
      configurations and based on the enabled address configuration
      modes on the access link, the mobility entities in the network can
      be certain about the exact address(es) configured by the mobile
      node.

   Mobile Node's Home Link

      This is the link on which the mobile node obtained its layer-3
      address configuration for the attached interface after it moved
      into that Proxy Mobile IPv6 domain.  This is the link that
      conceptually follows the mobile node.  The network will ensure the
      mobile node always sees this link with respect to the layer-3
      network configuration, on any access link that it attaches to in
      that Proxy Mobile IPv6 domain.

   Multihomed Mobile Node

      A mobile node that connects to the same Proxy Mobile IPv6 domain
      through more than one interface and uses these interfaces
      simultaneously is referred to as a multihomed mobile node.

   Mobile Node Identifier (MN-Identifier)

      The identity of a mobile node in the Proxy Mobile IPv6 domain.
      This is the stable identifier of a mobile node that the mobility
      entities in a Proxy Mobile IPv6 domain can always acquire and use
      for predictably identifying a mobile node.  This is typically an
      identifier such as a Network Access Identifier (NAI) [RFC4282] or
      other identifier such as a Media Access Control (MAC) address.

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   Mobile Node Link-layer Identifier (MN-LL-Identifier)

      An identifier that identifies the attached interface of a mobile
      node.  For those interfaces that have a link-layer identifier,
      this identifier can be based on that.  The link-layer identifier,
      in some cases, is generated by the mobile node and conveyed to the
      mobile access gateway.  This identifier of the attached interface
      must be stable, as seen by any of the mobile access gateways in a
      given Proxy Mobile IPv6 domain.  In some other cases, there might
      not be any link-layer identifier associated with the mobile node's
      interface.  An identifier value of ALL_ZERO is not considered a
      valid identifier and cannot be used as an interface identifier.

   Policy Profile

      Policy Profile is an abstract term for referring to a set of
      configuration parameters that are configured for a given mobile
      node.  The mobility entities in the Proxy Mobile IPv6 domain
      require access to these parameters for providing the mobility
      management to a given mobile node.  The specific details on how
      the network entities obtain this policy profile is outside the
      scope of this document.

   Proxy Binding Update (PBU)

      A request message sent by a mobile access gateway to a mobile
      node's local mobility anchor for establishing a binding between
      the mobile node's home network prefix(es) assigned to a given
      interface of a mobile node and its current care-of address (Proxy-
      CoA).

   Proxy Binding Acknowledgement (PBA)

      A reply message sent by a local mobility anchor in response to a
      Proxy Binding Update message that it received from a mobile access
      gateway.

   Per-MN-Prefix and Shared-Prefix Models

      The term Per-MN-Prefix model is used to refer to an addressing
      model where there is a unique network prefix or prefixes assigned
      for each node.  The term Shared-Prefix model is used to refer to
      an addressing model where the prefix(es) are shared by more than
      one node.  This specification supports the Per-MN-Prefix model and
      does not support the Shared-Prefix model.

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   Mobility Session

      In the context of Proxy Mobile IPv6 specification, the term
      mobility session refers to the creation or existence of state
      associated with the mobile node's mobility binding on the local
      mobility anchor and on the serving mobile access gateway.

   DHCP

      Throughout this document, the acronym DHCP refers to DHCP for
      IPv6, as defined in [RFC3315].

   ALL_ZERO and NON_ZERO

      Protocol message fields initialized with value 0 in each byte of
      the field.  For example, an 8-byte link-layer identifier field
      with the value set to 0 in each of the 8 bytes, or an IPv6 address
      with the value 0 in all of the 16 bytes.  Conversely, the term
      NON_ZERO is used to refer to any value other than an ALL_ZERO
      value.

3.  Proxy Mobile IPv6 Protocol Overview

   This specification describes a network-based mobility management
   protocol.  It is called Proxy Mobile IPv6 and is based on Mobile IPv6
   [RFC3775].

   Proxy Mobile IPv6 protocol is intended for providing network-based IP
   mobility management support to a mobile node, without requiring the
   participation of the mobile node in any IP mobility related
   signaling.  The mobility entities in the network will track the
   mobile node's movements and will initiate the mobility signaling and
   set up the required routing state.

   The core functional entities in the NETLMM infrastructure are the
   Local Mobility Anchor (LMA) and the Mobile Access Gateway (MAG).  The
   local mobility anchor is responsible for maintaining the mobile
   node's reachability state and is the topological anchor point for the
   mobile node's home network prefix(es).  The mobile access gateway is
   the entity that performs the mobility management on behalf of a
   mobile node, and it resides on the access link where the mobile node
   is anchored.  The mobile access gateway is responsible for detecting
   the mobile node's movements to and from the access link and for
   initiating binding registrations to the mobile node's local mobility
   anchor.  There can be multiple local mobility anchors in a Proxy
   Mobile IPv6 domain each serving a different group of mobile nodes.
   The architecture of a Proxy Mobile IPv6 domain is shown in Figure 1.

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              +----+                +----+
              |LMA1|                |LMA2|
              +----+                +----+
       LMAA1 -> |                      | <-- LMAA2
                |                      |
                \\                    //\\
                 \\                  //  \\
                  \\                //    \\
               +---\\------------- //------\\----+
              (     \\  IPv4/IPv6 //        \\    )
              (      \\  Network //          \\   )
               +------\\--------//------------\\-+
                       \\      //              \\
                        \\    //                \\
                         \\  //                  \\
             Proxy-CoA1--> |                      | <-- Proxy-CoA2
                        +----+                 +----+
                        |MAG1|-----{MN2}       |MAG2|
                        +----+    |            +----+
                          |       |               |
             MN-HNP1 -->  |     MN-HNP2           | <-- MN-HNP3, MN-HNP4
                        {MN1}                   {MN3}

                    Figure 1: Proxy Mobile IPv6 Domain

   When a mobile node enters a Proxy Mobile IPv6 domain and attaches to
   an access link, the mobile access gateway on that access link, after
   identifying the mobile node and acquiring its identity, will
   determine if the mobile node is authorized for the network-based
   mobility management service.

   If the network determines that the mobile node is authorized for
   network-based mobility service, the network will ensure that the
   mobile node using any of the address configuration mechanisms
   permitted by the network will be able to obtain the address
   configuration on the connected interface and move anywhere in that
   Proxy Mobile IPv6 domain.  The obtained address configuration
   includes the address(es) from its home network prefix(es), the
   default-router address on the link, and other related configuration
   parameters.  From the perspective of each mobile node, the entire
   Proxy Mobile IPv6 domain appears as a single link, the network
   ensures that the mobile node does not detect any change with respect
   to its layer-3 attachment even after changing its point of attachment
   in the network.

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   The mobile node may be an IPv4-only node, IPv6-only node, or a dual-
   stack (IPv4/v6) node.  Based on the policy profile information that
   indicates the type of address or prefixes to be assigned for the
   mobile node in the network, the mobile node will be able to obtain an
   IPv4, IPv6, or dual IPv4/IPv6 address and move anywhere in that Proxy
   Mobile IPv6 domain.  However, this specification only supports IPv6
   address/prefix mobility with the transport network being IPv6.  The
   support for IPv4 addressing or an IPv4 transport network is specified
   in the companion document [IPV4-PMIP6].

   If the mobile node connects to the Proxy Mobile IPv6 domain through
   multiple interfaces and over multiple access networks, the network
   will allocate a unique set of home network prefixes for each of the
   connected interfaces.  The mobile node will be able to configure
   address(es) on those interfaces from the respective home network
   prefix(es).  However, if the mobile node performs a handoff by moving
   its address configuration from one interface to the other, and if the
   local mobility anchor receives a handoff hint from the serving mobile
   access gateway about the same, the local mobility anchor will assign
   the same home network prefix(es) that it previously assigned prior to
   the handoff.  The mobile node will also be able to perform a handoff
   by changing its point of attachment from one mobile access gateway to
   a different mobile access gateway using the same interface and will
   be able to retain the address configuration on the attached
   interface.

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  +-----+                +-----+                +-----+
  | MN  |                | MAG |                | LMA |
  +-----+                +-----+                +-----+
     |                      |                      |
 MN Attached                |                      |
     |                      |                      |
     |       MN Attached Event from MN/Network     |
     |        (Acquire MN-Id and Profile)          |
     |                      |                      |
     |--- Rtr Sol --------->|                      |
     |                      |                      |
     |                      |--- PBU ------------->|
     |                      |                      |
     |                      |                  Accept PBU
     |                      | (Allocate MN-HNP(s), Setup BCE and Tunnel)
     |                      |                      |
     |                      |<------------- PBA ---|
     |                      |                      |
     |                 Accept PBA                  |
     |          (Set Up Tunnel and Routing)        |
     |                      |                      |
     |                      |==== Bi-Dir Tunnel ===|
     |                      |                      |
     |<--------- Rtr Adv ---|                      |
     |                      |                      |
  IP Address                |                      |
 Configuration              |                      |
     |                      |                      |

          Figure 2: Mobile Node Attachment - Signaling Call Flow

   Figure 2 shows the signaling call flow when the mobile node enters
   the Proxy Mobile IPv6 domain.  The Router Solicitation message from
   the mobile node may arrive at any time after the mobile node's
   attachment and has no strict ordering relation with the other
   messages in the call flow.

   For updating the local mobility anchor about the current location of
   the mobile node, the mobile access gateway sends a Proxy Binding
   Update message to the mobile node's local mobility anchor.  Upon
   accepting this Proxy Binding Update message, the local mobility
   anchor sends a Proxy Binding Acknowledgement message including the
   mobile node's home network prefix(es).  It also creates the Binding
   Cache entry and sets up its endpoint of the bi-directional tunnel to
   the mobile access gateway.

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   The mobile access gateway on receiving the Proxy Binding
   Acknowledgement message sets up its endpoint of the bi-directional
   tunnel to the local mobility anchor and also sets up the forwarding
   for the mobile node's traffic.  At this point, the mobile access
   gateway has all the required information for emulating the mobile
   node's home link.  It sends Router Advertisement messages to the
   mobile node on the access link advertising the mobile node's home
   network prefix(es) as the hosted on-link prefix(es).

   The mobile node, on receiving these Router Advertisement messages on
   the access link, attempts to configure its interface using either
   stateful or stateless address configuration modes, based on the modes
   that are permitted on that access link as indicated in Router
   Advertisement messages.  At the end of a successful address
   configuration procedure, the mobile node has one or more addresses
   from its home network prefix(es).

   After address configuration, the mobile node has one or more valid
   addresses from its home network prefix(es) at the current point of
   attachment.  The serving mobile access gateway and the local mobility
   anchor also have proper routing states for handling the traffic sent
   to and from the mobile node using any one or more of the addresses
   from its home network prefix(es).

   The local mobility anchor, being the topological anchor point for the
   mobile node's home network prefix(es), receives any packets that are
   sent to the mobile node by any node in or outside the Proxy Mobile
   IPv6 domain.  The local mobility anchor forwards these received
   packets to the mobile access gateway through the bi-directional
   tunnel.  The mobile access gateway on other end of the tunnel, after
   receiving the packet, removes the outer header and forwards the
   packet on the access link to the mobile node.  However, in some
   cases, the traffic sent from a correspondent node that is locally
   connected to the mobile access gateway may not be received by the
   local mobility anchor and may be routed locally by the mobile access
   gateway (refer to Section 6.10.3).

   The mobile access gateway acts as the default router on the point-to-
   point link shared with the mobile node.  Any packet that the mobile
   node sends to any correspondent node will be received by the mobile
   access gateway and will be sent to its local mobility anchor through
   the bi-directional tunnel.  The local mobility anchor on the other
   end of the tunnel, after receiving the packet, removes the outer
   header and routes the packet to the destination.  However, in some
   cases, the traffic sent to a correspondent node that is locally
   connected to the mobile access gateway may be locally routed by the
   mobile access gateway (refer to Section 6.10.3).

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    +-----+          +-----+          +-----+          +-----+
    | MN  |          |p-MAG|          | LMA |          |n-MAG|
    +-----+          +-----+          +-----+          +-----+
       |                |                |                |
       |                |==Bi-Dir Tunnel=|                |
   MN Detached          |                |                |
       |         MN Detached Event       |                |
       |                |                |                |
       |                |-- DeReg PBU -->|                |
       |                |                |                |
       |                |            Accept PBU           |
       |                |   (Start MinDelayBeforeBCEDelete Timer)
       |                |                |                |
       |                |<-------- PBA --|                |
       |                |                |                |
   MN Attached          |                |                |
       |                |                |   MN Attached event received
       |                |                |     from MN or from network
       |                |                |   (Acquire MN-Id and Profile)
       |                |                |                |
       |--- Rtr Sol ------------------------------------->|
                               ....
                                    Registration steps as in Fig. 2.
                               ....
       |                |                |==Bi-Dir Tunnel=|
       |                |                |                |
       |<------------------------------------ Rtr Adv ----|
       |                |                |                |
   MN retains HoA/HNP(s)
       |                |                |                |

            Figure 3: Mobile Node Handoff - Signaling Call Flow

   Figure 3 shows the signaling call flow for the mobile node's handoff
   from the previously attached mobile access gateway (p-MAG) to the
   newly attached mobile access gateway (n-MAG).  This call flow only
   reflects a specific message ordering, it is possible the registration
   message from the n-MAG may arrive before the de-registration message
   from the p-MAG arrives.

   After obtaining the initial address configuration in the Proxy Mobile
   IPv6 domain, if the mobile node changes its point of attachment, the
   mobile access gateway on the previous link will detect the mobile
   node's detachment from the link.  It will signal the local mobility
   anchor and will remove the binding and routing state for that mobile
   node.  The local mobility anchor, upon receiving this request, will
   identify the corresponding mobility session for which the request was

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   received, and accepts the request after which it waits for a certain
   amount of time to allow the mobile access gateway on the new link to
   update the binding.  However, if it does not receive any Proxy
   Binding Update message within the given amount of time, it will
   delete the binding cache entry.

   The mobile access gateway on the new access link, upon detecting the
   mobile node on its access link, will signal the local mobility anchor
   to update the binding state.  After completion of the signaling, the
   serving mobile access gateway will send the Router Advertisements
   containing the mobile node's home network prefix(es), and this will
   ensure the mobile node will not detect any change with respect to the
   layer-3 attachment of its interface.

4.  Proxy Mobile IPv6 Protocol Security

   The signaling messages, Proxy Binding Update, and Proxy Binding
   Acknowledgement, exchanged between the mobile access gateway and the
   local mobility anchor, MUST be protected using end-to-end security
   association(s) offering integrity and data origin authentication.

   The mobile access gateway and the local mobility anchor MUST
   implement IPsec for protecting the Proxy Mobile IPv6 signaling
   messages [RFC4301].  IPsec is a mandatory-to-implement security
   mechanism.  However, additional documents may specify alternative
   mechanisms and the mobility entities can enable a specific mechanism
   for securing Proxy Mobile IPv6 signaling messages, based on either a
   static configuration or after a dynamic negotiation using any
   standard security negotiation protocols.  As in Mobile IPv6
   [RFC3775], the use of IPsec for protecting a mobile node's data
   traffic is optional.

   IPsec Encapsulating Security Payload (ESP) [RFC4303] in transport
   mode with mandatory integrity protection SHOULD be used for
   protecting the signaling messages.  Confidentiality protection of
   these messages is not required.

   IPsec ESP [RFC4303] in tunnel mode MAY be used to protect the mobile
   node's tunneled data traffic, if protection of data traffic is
   required.

   Internet Key Exchange Protocol version 2 (IKEv2) [RFC4306] SHOULD be
   used to set up security associations between the mobile access
   gateway and the local mobility anchor to protect the Proxy Binding
   Update and Proxy Binding Acknowledgement messages.  The mobile access
   gateway and the local mobility anchor can use any of the
   authentication mechanisms, as specified in [RFC4306], for mutual
   authentication.

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   The Mobile IPv6 specification [RFC3775] requires the home agent to
   prevent a mobile node from creating security associations or creating
   binding cache entries for another mobile node's home address.  In the
   protocol described in this document, the mobile node is not involved
   in creating security associations for protecting the signaling
   messages or sending binding updates.  Therefore, the local mobility
   anchor MUST restrict the creation and manipulation of proxy bindings
   to specifically authorized mobile access gateways and prefixes.  The
   local mobility anchor MUST be locally configurable to authorize such
   specific combinations.  Additional mechanisms, such as a policy store
   or Authentication, Authorization, and Accounting (AAA) may be
   employed, but these are outside the scope of this specification.

   Unlike in Mobile IPv6 [RFC3775], these signaling messages do not
   carry either the Home Address destination option or the Type 2
   Routing header, and hence the policy entries and security association
   selectors stay the same and require no special IPsec related
   considerations.

4.1.  Peer Authorization Database (PAD) Example Entries

   This section describes PAD entries [RFC4301] on the mobile access
   gateway and the local mobility anchor.  The PAD entries are only
   example configurations.  Note that the PAD is a logical concept and a
   particular mobile access gateway or a local mobility anchor
   implementation can implement the PAD in any implementation-specific
   manner.  The PAD state may also be distributed across various
   databases in a specific implementation.

   In the example shown below, the identity of the local mobility anchor
   is assumed to be lma_identity_1 and the identity of the mobile access
   gateway is assumed to be mag_identity_1.

       mobile access gateway PAD:
         - IF remote_identity = lma_identity_1
              Then authenticate (shared secret/certificate/EAP)
              and authorize CHILD_SAs for remote address lma_address_1

       local mobility anchor PAD:
         - IF remote_identity = mag_identity_1
              Then authenticate (shared secret/certificate/EAP)
              and authorize CHILD_SAs for remote address mag_address_1

                           Figure 4: PAD Entries

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   The list of authentication mechanisms in the above examples is not
   exhaustive.  There could be other credentials used for authentication
   stored in the PAD.

4.2.  Security Policy Database (SPD) Example Entries

   This section describes the security policy entries [RFC4301] on the
   mobile access gateway and the local mobility anchor required to
   protect the Proxy Mobile IPv6 signaling messages.  The SPD entries
   are only example configurations.  A particular mobile access gateway
   or a local mobility anchor implementation could configure different
   SPD entries as long as they provide the required security.

   In the example shown below, the identity of the mobile access gateway
   is assumed to be mag_identity_1, the address of the mobile access
   gateway is assumed to be mag_address_1, and the address of the local
   mobility anchor is assumed to be lma_address_1.  The acronym MH
   represents the protocol number for the Mobility Header [RFC3775],
   while the terms local_mh_type and remote_mh_type stand for local
   mobility header type and remote mobility header type, respectively.

      mobile access gateway SPD-S:
        - IF local_address = mag_address_1 &
             remote_address = lma_address_1 &
             proto = MH & (local_mh_type = BU | remote_mh_type = BA)
          Then use SA ESP transport mode
          Initiate using IDi = mag_identity_1 to address lma_address_1

      local mobility anchor SPD-S:
        - IF local_address = lma_address_1 &
             remote_address = mag_address_1 &
             proto = MH & (local_mh_type = BA | remote_mh_type = BU)
          Then use SA ESP transport mode

                           Figure 5: SPD Entries



(page 17 continued on part 2)

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